Calcitonin (CT) is a calcium-regulating hormone secreted by the thyroid in response to elevated blood calcium levels. It is also produced at low levels in several other tissues where it has been found to have local regulatory activity via paracrine or autocrine mechanisms. Recently I have found that CT is expressed in mammary glandular epithelial tissue during late pregnancy and decreases at birth. Mammary tissue also expresses receptors for CT, suggesting that the hormone acts locally. Because extensive alveolar proliferation and differentiation occurs during late pregnancy, I hypothesize that CT may have a role in this process. Supporting this, may laboratory has seen that non-pregnant mice treated with CT show increased lobular budding and mammary development. CT also has been seen to regulate proliferation of breast cancer cell lines. Gaining an understanding of the effect of CT on mammary development may therefore shed light both on the hormonal control of normal development and factors involved in breast cancer growth. To investigate the action of mammary CT, students will have individual projects in the following areas: - Characterizing the expression of CT and its receptor in mammary tissue using northern blot, western blot and in situ hybridization analysis. -Further characterization of CT regulation of mammogenesis in vivo and in vitro -Testing the hypothesis that CT stimulation of mammogenesis occurs through elevation of mammary cAMP levels.